Fish, especially trout, eat insects native to streams and lakes in which they live. One catching strategy is to use artificial flies that mimic the natural prey insects. Many of these insects are small and float on the surface. Certain considerations and techniques are required in fly fishing gear design for effective mimicking of natural insect activity.
One key consideration is the role and placement of weight. The artificial lures ("flies") used in flyfishing must be virtually weightless and the line must be designed to deliver the fly to the water surface with as gentle a landing as is performed by a real insect. Usually, a line is used that exhibits a multiple or compound taper. It tapers from a relatively larger diameter at the belly to a relatively small diameter at the tip. Other taper configurations are employed for affecting reel capacity, line reversibility, or casting performance.
Anglers also wish to mimic prey insects that could float as well as those that would sink. With the degree of precision required by expert fly angler, however, it was imperative that a line represented to be a floating line was actually able to float over the life of the line and that were supposed to sink would sink appropriately. Since few, if any, of the pre-1940 silk, linen, or horsehair-containing lines was able to float, the line surface was treated ("dressed") with wax, muscilin, or paraffin to make them water repellant. Because these early lines were susceptible to rotting and required routine cleaning, the integrity of the water repellant dressing was critical to the useful life of flylines.
In the 1940's, synthetic line materials became available. These new materials permitted new flyline opportunities. For example, the prior natural line dressings could now be replaced with an overcoat of synthetic buoyant materials that would not suffer the drawbacks of the natural dressing materials. Nylon lines were used for floating lines. Polyester was used for sinking lines.
Tapering the early lines was accomplished by a painstakingly labor intensive process based on splicing together fibers of reducing diameters to achieve the taper, e.g., Miller et al. U.S. Pat. No. 2,933,798. This process established a high price for such lines and taught line designers about the interactions among weight distribution, casting ease, and casting distance. All of the post-1940 lines were based on a central line for strength and flexibility with buoyant coatings to improve float characteristics. Although solid monofilaments were suggested as useful in some of the early patents, the need for core lines with low stretch, an air evacuation route, and minimum flexibility requirements dictated that hollow braids became the state of the art as the core for modern flylines.
Martuch U.S. Pat. No. 3,043,045 teaches the use of a level braided core covered by a tapering plasticized polyvinyl chloride ("plastisol") coating that contained glass microballoons to reduce the density of the plastisol. An adhesive primer was used to adhere the soft plastisol layer to the core line. See also, Richardson et al. U.S. Pat. No. 3,486,266 (glass microspheres in plastisol), Coilingbourne U.S. Pat. No. 3,830,009 (blown or gas-expanded plastic coating over a multifiber braided core), Lang U.S. Pat. No. 3,914,480 (incorporate tougher monomer into plastisol for increased abrasion resistance), and Martuch U.S. Pat. No. 3,936,335 (add foamed material to core under plastisol/microsphere coating).
Polymeric, buoyant coatings could be tapered by mechanical means to produce finished products in a heat cured process at or above about 300.degree. F. and provided a number of options not previously available. Plasticizers tailored flexibility. Colors could be added with dyes and pigments. Lubricants could be added to the plastisol. High density metal powders could be added in place of glass microspheres for sinking lines.
FIG. 1 shows a typical prior art flyline. Braided core 1 typically measures about 0.018-0.030 inches (457-762 nm) and is chosen to maintain structural integrity throughout the curing process and provide the basic strength of the line. Adhesive layer 2 (sometimes referred to as a "primer") covers core 1 and is itself coated with polymeric overcoat 3. Overcoat 3 typically contains levels of glass microballoons of about 20-120 nm in diameter or a dense powder (e.g., rungsten) in a quantity to adjust the buoyancy characteristics of the flyline to float or sink at predesignated rates. Additionally, silicone lubricants are used to reduce surface friction, and coloring agents are added to adjust the appearance of the flyline.
Despite the better performance, the modern flylines still suffer a number of drawbacks and shortcomings. Some problems include:
1. Tip sinking in floating lines. Experience has shown that the core line must be a hollow braid. Heat used in the curing process for the plastisol expands any air around the core. Unless that air is allowed to vent through a hollow core, the gas expands into the plastisol and causes a bubble defect. Unfortunately, hollow braids inherently provide a surface into which water will wick thereby changing the density and causing the tip to sink. Braided core lines must be treated with waterproofing materials to resist wicking. Such coatings have had limited success, and tip sinking remains a major complaint of modern flylines.
2. Surface cracking. The glass microspheres commonly used do not bond well to the plastisol matrix. Sizing agent can help, but the constant flexing of the line during use results in cracks between the microspheres and the matrix. These cracks propagate with additional flexing thereby creating a "hinge" effect that affects "turnover" and casting performance. Water penetrates these cracks and worsens the sinking effects.
3. Limited durability. Plasticizers used to make the line sufficiently flexible to reduce surface cracking and facilitate casting also soften the polymer. The use of higher levels of glass microspheres for buoyancy also stiffens the line as well as increasing its tendency to crack. Each flyline is its manufacturer's compromise of durability, flexibility, buoyancy, and vulnerability toward cracking.
4. Memory. The adhesive used to promote the bond between the core and the plastisol allows relative movement when stored in a coiled state over time ("creep") thus giving what is known as a line "memory." Lines with memory are characterized by a coiled shape as the line leaves the reel. Because the line should unwind straight, fly angler often stretch their entire line lengths before each season to remove the line storage memory effect. Without adhesive, however, the normal plastisol coating can be readily removed from the core with relatively little effort. One commercial attempt to make lines of a polyaramid core and a polyurethane coating without an adhesive between the core and the coating exhibited excessive slippage between the core and the overcoat. Modern lines use adhesives requiring a balance between memory and durability as a critical compromise.
5. Surface friction. The normal, flexible plastisol has a relatively high degree of surface friction and casting resistance. A surface dressing is usually applied by either the manufacturer or the angler to lower the surface friction and improve casting distance. Although these surface dressings help, they also allow foreign material to adhere to the surface which can enhance abrasion and sinking problems. More flexibility means softer surfaces and increased durability and friction concerns.
6. Solvent effects. Plasticizers are frequently solvents that chemically attack the commonly used packaging materials. Relatively expensive spool and packaging materials must be used.
7. Relatively high scrap rates in premium flylines. The formulation of plastisol for flylines is as much of an art as a science. The plastisol viscosity varies with the formulation as well as with age of batch. Core braid irregularities may be seen in coated products. Core centering is critical and difficult. In addition, surface blemishes may lead to unacceptable lines. Unfortunately, scrap rates for flylines are fairly high due to such defects.
It would be desirable to have a flexible flyline that avoided, eliminated, or at least reduced the persistent problems with prior art flylines.